title: Clinical, morphologic, and immunohistochemical features of canine orbital hibernomas.
abstract: Hibernomas are uncommon benign tumors of brown fat that occur in humans and various animal species. They have not been observed in the orbit of dogs, humans, or other animals. Here we report clinical, light and electron microscopic, and immunohistochemical features of a series of 7 hibernomas arising in the orbital region of dogs. These neoplasms occurred in adult dogs with no breed predilection. The mean age of the affected dogs was 10.4 years (range, 8-13 years). All neoplasms presented as soft lobular masses composed of predominantly round or polygonal neoplastic cells with granular eosinophilic and vacuolated cytoplasm resembling adipocytes. The cytoplasm contained large numbers of pleomorphic mitochondria with dense matrices and indistinct cristae. Immunohistochemical evaluation confirmed positive labeling of neoplastic cells from all cases with uncoupling protein 1 (UCP-1) consistent with brown fat differentiation. Interestingly, rare neoplastic cells also expressed myogenin and myoD, possibly suggesting a common progenitor cell for neoplastic brown adipose and skeletal muscle cells.
authors.affiliation: Alberta Agriculture and Rural Development, OS Longman Bldg, 6909 112 St, Edmonton, Alberta T6H 4P2, Canada. Email: madhu.ravi@gov.ab.ca.
authors.forename: M
authors.initials: M
authors.lastname: Ravi
authors.forename: C S
authors.initials: CS
authors.lastname: Schobert
authors.forename: M
authors.initials: M
authors.lastname: Kiupel
authors.forename: R R
authors.initials: RR
authors.lastname: Dubielzig
mesh_terms: D052437:Adipocytes, Brown / Q000378:metabolism / Q000648:ultrastructure; D000818:Animals; D004283:Dog Diseases / Q000378:metabolism / Q000473:pathology*; D004285:Dogs; D007150:Immunohistochemistry / Q000662:veterinary; D007473:Ion Channels / Q000378:metabolism; D008067:Lipoma / Q000473:pathology / Q000662:veterinary*; D046529:Microscopy, Electron, Transmission; D024101:Mitochondrial Proteins / Q000378:metabolism; D009918:Orbital Neoplasms / Q000378:metabolism / Q000473:pathology / Q000662:veterinary*; D000071256:Uncoupling Protein 1
chemical_list: D007473:Ion Channels; D024101:Mitochondrial Proteins; C000604371:UCP1 protein, human; D000071256:Uncoupling Protein 1
keywords: MyoD; UCP1; brown adipose tissue; hibernoma; immunohistochemistry; lipomatous tumors; liposarcoma; myogenin